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Wang Y, Dong L, Li J, Luo M, Shang B. Pentoxifylline induces apoptosis of HepG2 cells by reducing reactive oxygen species production and activating the MAPK signaling. Life Sci 2017; 183:60-68. [DOI: 10.1016/j.lfs.2017.05.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 05/25/2017] [Accepted: 05/31/2017] [Indexed: 02/07/2023]
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Fukazawa K, Vitin AA, Pretto EA. Serum acidosis prior to reperfusion facilitates hemodynamic recovery following liver transplantation. J Anesth 2015; 30:80-8. [PMID: 26449675 DOI: 10.1007/s00540-015-2080-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 09/18/2015] [Indexed: 11/28/2022]
Abstract
INTRODUCTION Reperfusion is the most critical event during liver transplantation, and sustained leakage of acidic preservation solution from the liver graft contributes to marked hemodynamic instability. Recent laboratory studies with hepatocyte cultures have revealed that low pH may protect hepatocyte mitochondria against ischemia-reperfusion injury by inhibiting the mitochondrial permeability transition (MPT), the so-called "pH paradox." However, the clinical significance of this pH paradox theory remains largely unknown. In this study, we sought to determine whether there is an association between serum pH immediately prior to reperfusion and hemodynamic recovery after reperfusion and graft survival. METHODS We analyzed retrospective data from 527 patients who underwent Orthotopic liver transplantation between 2003 and 2008. All patients were allocated to one of two groups: pH ≤ 7.32 or pH > 7.32, as measured 5 min before reperfusion. Case-control matching was performed using the propensity score to adjust for background differences between the two groups. Data were analyzed using Student's t-test and the χ (2) test. RESULTS There were 85 patients in the pH ≤ 7.32 group and 385 patients in the pH > 7.32 group. The recovery of mean arterial pressure after hepatic artery reperfusion was significantly faster in the pH ≤ 7.32 group (slope of recovery: 0.0004 % vs. 0.0002 %/min, p = 0.041). Other parameters studied, including vasopressor dosage after reperfusion, did not show any statistically significant difference between groups. CONCLUSIONS Our findings suggest that less aggressive treatment of acidosis with a slower rate of normalization of serum pH (from low to normal) after reperfusion promotes faster hemodynamic stabilization. These findings provide evidence to support the concept of the pH paradox, and may also substantiate the argument against the usage of alkalizing agents before reperfusion unless acidosis becomes clinically significant.
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Affiliation(s)
- Kyota Fukazawa
- Division of Transplant Anesthesia, Department of Anesthesiology and Pain Medicine, University of Washington, School of Medicine, 1959 NE Pacific Street, Seattle, WA, 98195, USA.
| | - Alexander A Vitin
- Division of Transplant Anesthesia, Department of Anesthesiology and Pain Medicine, University of Washington, School of Medicine, 1959 NE Pacific Street, Seattle, WA, 98195, USA
| | - Ernesto A Pretto
- Division of Solid Organ Transplantation, Department of Anesthesiology, University of Miami, Leonard Miller School of Medicine, Miami, FL, USA
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Berendsen TA, Izamis ML, Xu H, Liu Q, Hertl M, Berthiaume F, Yarmush ML, Uygun K. Hepatocyte viability and adenosine triphosphate content decrease linearly over time during conventional cold storage of rat liver grafts. Transplant Proc 2011; 43:1484-8. [PMID: 21693222 DOI: 10.1016/j.transproceed.2010.12.066] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Accepted: 12/20/2010] [Indexed: 01/29/2023]
Abstract
INTRODUCTION The gold standard in organ preservation is static cold storage (SCS) using University of Wisconsin solution (UW). Although it is well-known that there is a finite limit to SCS preservation, and that there is a correlation between the adenosine triphosphate (ATP) levels and organ function post-preservation, a quantitative relationship has not been established, which is important in understanding the fundamental limitations to preservation, minimizing cold ischemic injury, and hence maximizing use of the donor organ pool. AIM This study determines the time limits of cellular viability and metabolic function during SCS, and characterizes the relationship between cellular viability and energetic state using clinically relevant techniques in organ preservation. METHODS Rat livers were procured and stored using conventional storage in UW solution at 4 °C. Viability was assessed by determining the amount of viable hepatocytes and intracellular ATP content after 0, 24, 48, 72, and 120 hours of storage. RESULTS Numbers of viable hepatocytes that were isolated from these livers decreased steadily during SCS. After 5 days, viable hepatocytes decreased from 25.95 × 10(6) to 0.87 × 10(6) cells/gram tissue. Intracellular ATP content decreased from 9.63 to 0.93 moles/g tissue. Statistical analysis of variance established a linear relation for both parameters as a function of time (P < .05). CONCLUSION The linear correlation between hepatocyte viability, ATP content, and storage time suggests a shared physiological foundation. These findings confirm ATP as direct predictor for organ quality in the context of liver preservation, which will aid quantitative assessment of donor organs for various applications.
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Affiliation(s)
- T A Berendsen
- Center for Engineering in Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and Shriners Burns Hospital, Boston, Massachusetts 02114, USA
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c-Jun Terminal Kinase-2 Gene Deleted Mice Overexpress Hemeoxygenase-1 and Are Protected From Hepatic Ischemia Reperfusion Injury. Transplantation 2009; 88:308-16. [DOI: 10.1097/tp.0b013e3181ae3067] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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BOND JOHNM, HARPER IANS, CHACON ENRIQUE, REECE JEFFREYM, HERMAN BRIAN, LEMASTERS JOHNJ. The pH Paradox in the Pathophysiology of Reperfusion Injury to Rat Neonatal Cardiac Myocytes a. Ann N Y Acad Sci 2006. [DOI: 10.1111/j.1749-6632.1994.tb36714.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Marian CF, Jiga LP, Ionac M. Ischemic preconditioning of free muscle flaps: An experimental study. Microsurgery 2005; 25:524-31. [PMID: 16184525 DOI: 10.1002/micr.20158] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aim of this study was to apply the hypothesis of ischemic preconditioning (IP) on free skeletal muscle (rat thigh flap). Five groups of Sprague-Dawley rats (n = 6) were used. In group A (control group), standard free autologous flap transfers were performed. Flaps in groups B and C underwent 4 and 6 h, respectively, of ischemia before transfer. In groups D and E, muscle flaps were preconditioned (3 x 10 min ischemia interrupted by 10 min of reperfusion, clip applied on the dissected artery of the flap) and subjected to 4 and 6 h, respectively, of ischemia before transfer. After 48 h of reperfusion, the muscle flaps were evaluated macroscopically as well as by histological and immunohystochemical staining. In group A, the viability was 100%, whereas in groups D and E the viability was 83.3% and 100%, respectively. Groups B and C had undergone macroscopically parceled to total necrosis, further confirmed by histological findings (fragmentation and disappearance of muscle striations, combined with tissue necrosis and intravascular thrombosis). The beneficial effect of IP demonstrated in the heart, liver, and small bowel extends to skeletal muscle, which can be used in free-flap transfers, if the transfer includes a long period of predictable ischemia.
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Affiliation(s)
- Claudiu F Marian
- Center for Laparoscopic Surgery and Microsurgery Pius Brânzeu, University of Medicine and Pharmacy Victor Babes, Timisoara, Romania
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Lambert JC, Zhou Z, Wang L, Song Z, McClain CJ, Kang YJ. Prevention of alterations in intestinal permeability is involved in zinc inhibition of acute ethanol-induced liver damage in mice. J Pharmacol Exp Ther 2003; 305:880-6. [PMID: 12626662 DOI: 10.1124/jpet.102.047852] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Acute ethanol exposure causes liver injury in experimental animals, and accumulating evidence suggests that a major responsible factor for the pathogenesis is endotoxemia, which results from bacterial endotoxin leakage from the small intestine due to increased intestinal permeability under alcohol challenge. The purpose of this study was to examine whether zinc pretreatment would inhibit acute ethanol-induced liver injury through prevention of intestinal permeability changes. Male 129 SvPCJ mice were treated with three intragastric doses of ZnSO4 at 5 mg of zinc ion per kg each dosing prior to acute ethanol challenge with a single oral dose of 6 g/kg ethanol. The zinc treatment did not alter the elevation of serum concentrations of alcohol. The acute ethanol exposure caused an elevation in serum alanine aminotransferase levels as well as fatty liver and hepatic degenerative necrotic foci as determined by biochemical assay and histochemical analysis, respectively. A significant increase in liver tumor necrosis factor-alpha (TNF-alpha) levels was detected by enzyme-linked immunosorbent assay. These pathological effects correlated well with increases in serum endotoxin levels. Importantly, acute ethanol treatment caused significant damage to the small intestine as determined by morphological analysis of intestinal sections and permeability assay. These alcohol-induced hepatic pathological changes and TNF-alpha elevation were significantly inhibited in the zinc-pretreated animals. The inhibitory action of zinc on alcohol-induced liver damage and activation of inflammation was associated with zinc suppression of alcohol-induced intestinal permeability changes. These results thus demonstrate that zinc prevention of increased intestinal permeability is importantly involved in the inhibition of acute ethanol-induced liver damage in mice.
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Affiliation(s)
- Jason C Lambert
- Department of pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY 40202, USA
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Fabia R, Travis DL, Levy MF, Husberg BS, Goldstein RM, Klintmalm GB. Effect of pentoxifylline on hepatic ischemia and reperfusion injury. Surgery 1997; 121:520-5. [PMID: 9142150 DOI: 10.1016/s0039-6060(97)90106-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Although pentoxifylline has been shown to improve tissue oxygenation and restore hepatocellular function after hemorrhagic shock, its effect on hepatic ischemia and reperfusion injury has not been fully clarified. The purpose of this study was to determine whether pentoxifylline exerted beneficial effects on liver histopathologic changes and enzymatic release caused by ischemia and reperfusion. METHODS Warm, reversible hepatic ischemia/reperfusion injury was induced in four groups of pigs. Preoperative oral (24 mg/kg or 50 mg/kg) or intraoperative intravenous (50 mg/kg) pentoxifylline was administered. Control animals received intravenous normal saline solution. RESULTS Untreated control animals exhibited significant liver damage expressed by hepatic histopathologic changes and high plasma levels of aminotransferases. Decreased animal survival was seen in the untreated group. All treated animals survived. Pentoxifylline given orally did not improve histopathologic changes or enzyme release. Intravenous administration caused significant amelioration of liver tissue damage, marked reduction of aspartate aminotransferase levels, and mild attenuation of alanine aminotransferase levels, as compared with control. CONCLUSIONS This study indicates that intraoperative, intravenous pentoxifylline reduces hepatic injury after warm ischemia and reperfusion.
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Affiliation(s)
- R Fabia
- Transplant Services, Baylor University Medical Center, Dallas, Texas 75246, USA
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Abstract
Preservation injury remains an obstacle to greater utilization of liver transplantation therapy. Livers can be preserved a maximum of 24 h in University of Wisconsin solution. After longer times, reperfusion precipitates endothelial cell killing and activation of Kupffer cells (liver macrophages). Together, Kupffer cell activation and endothelial cell killing cause microcirculatory disturbances, leukocyte and platelet adhesion, and a systemic inflammatory response after graft implantation. Down-regulation of Kupffer cells with calcium blockers or pentoxifylline improves graft survival, whereas priming with lipopolysaccharide or alcohol worsens survival. Flushing grafts after storage with Carolina rinse solution containing antioxidants, adenosine, calcium blocker, energy substrates, and glycine at pH 6.5 decreases endothelial cell killing, reduces Kupffer cell activation, and improves graft survival. Understanding of the roles of different cells in storage/reperfusion injury forms the basis for strategies to prolong organ storage, improve graft function, and reduce failure of fatty grafts from alcoholic donors.
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Affiliation(s)
- J J Lemasters
- Department of Cell Biology, School of Medicine, University of North Carolina, Chapel Hill 27599-7090, USA
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Lemasters JJ, Bond JM, Chacon E, Harper IS, Kaplan SH, Ohata H, Trollinger DR, Herman B, Cascio WE. The pH paradox in ischemia-reperfusion injury to cardiac myocytes. EXS 1996; 76:99-114. [PMID: 8805791 DOI: 10.1007/978-3-0348-8988-9_7] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
During myocardial ischemia, a large reduction of tissue pH develops, and tissue pH returns to normal after reperfusion. In recent studies, we evaluated the role of pH in ischemia/reperfusion injury to cultured cardiac myocytes and perfused papillary muscles. Acidosis (pH < or = 7.0) protected profoundly against cell death during ischemia. However, the return from acidotic to normal pH after reperfusion caused myocytes to lose viability. This worsening of injury is a 'pH paradox' and was mediated by changes of intracellular pH (pH(i)), since manipulations that caused pH(i), to increase more rapidly after reperfusion accelerated cell killing, whereas manipulations that delayed the increase of pH(i) prevented loss of myocyte viability. Specifically, inhibition of the Na+/H+ exchanger with dimethylamiloride or HOE694 delayed the return of physiologic pH(i) after reperfusion and prevented reperfusion-induced cell killing to both cultured myocytes and perfused papillary muscle. Dimethylamiloride and HOE694 did not reduce intracellular free Ca2+ during reperfusion. By contrast, reperfusion with dichlorobenzamil, an inhibitor of Na+/Ca2+ exchange, decreased free Ca2+ but did not reduce cell killing. Thus, the pH paradox is not Ca(2+)-dependent. Our working hypothesis is that ischemia activates hydrolytic enzymes, such as phospholipases and proteases, whose activity is inhibited at acidotic pH. Upon reperfusion, the return to normal pH releases this inhibition and hydrolytic injury ensues. Increasing pH(i) may also induce a pH-dependent mitochondrial permeability transition and activate the myofibrillar ATPase, effects that increase ATP demand and compromise ATP supply. In conclusion, acidotic pH is generally protective in ischemia, whereas a return to physiologic pH precipitates lethal reperfusion injury to myocytes.
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Affiliation(s)
- J J Lemasters
- Department of Cell Biology and Anatomy, University of North Carolina at Chapel Hill 27599-7090, USA
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Lemasters JJ, Bunzendahl H, Thurman RG. Reperfusion injury to donor livers stored for transplantation. LIVER TRANSPLANTATION AND SURGERY : OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION FOR THE STUDY OF LIVER DISEASES AND THE INTERNATIONAL LIVER TRANSPLANTATION SOCIETY 1995; 1:124-38. [PMID: 9346554 DOI: 10.1002/lt.500010211] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- J J Lemasters
- Department of Cell Biology & Anatomy, School of Medicine, University of North Carolina, Chapel Hill 27599-7090, USA
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Caldwell-Kenkel JC, Currin RT, Coote A, Thurman RG, Lemasters JJ. Reperfusion injury to endothelial cells after cold storage of rat livers: protection by mildly acidic pH and lack of protection by antioxidants. Transpl Int 1995; 8:77-85. [PMID: 7766302 DOI: 10.1007/bf00344415] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Lethal reperfusion injury to sinusoidal endothelial cells occurs after cold ischemic storage of livers and may be responsible for liver graft failure from storage injury. Here, we evaluated potential mechanisms underlying this reperfusion injury. In rat livers stored in Euro-Collins solution for 24 h and reperfused with Krebs-Henseleit bicarbonate buffer, nonparenchymal cell killing showed periportal predominance as assessed by nuclear staining with trypan blue. In livers reperfused in the retrograde direction, the lobular distribution of cell killing was reversed, indicating that cell killing was more rapid in oxygen-rich upstream regions. However, antioxidants, including allopurinol, desferrioxamine, catalase, superoxide dismutase, superoxide dismutase plus catalase, and U74006F, did not reduce cell killing. Similarly, reperfusion with anoxic buffer did not prevent lethal injury. Antioxidants and anoxic reperfusion also did not improve cell viability in livers stored in UW solution. Nevertheless, superoxide generation, as identified by formazan formation from nitroblue tetrazolium, was increased in Kupffer cells after lives storage and reperfusion as compared to unstored livers. Acidification of the reperfusion buffer from pH 7.4 to pH 7.15 reduced overall nonparenchymal cell killing from about 40% to 10%. Moreover, a pH gradient developed across the liver lobule during reperfusion with the effluent 0.2-0.4 pH units more acidic than the influent. This intralobular pH gradient appears to account for the relative sparing of cells in more acidic downstream regions of the lobule. Lower temperatures of reperfusion also reduced lethal injury. In conclusion, Kupffer cells generated superoxide after perfusion of stored rat livers, but formation of oxygen free radicals did not appear to contribute to lethal reperfusion injury to endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J C Caldwell-Kenkel
- Department of Cell Biology & Anatomy, University of North Carolina at Chapel Hill 27599-7090, USA
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Adachi Y, Bradford BU, Gao W, Bojes HK, Thurman RG. Inactivation of Kupffer cells prevents early alcohol-induced liver injury. Hepatology 1994. [PMID: 8045507 DOI: 10.1002/hep.1840200227] [Citation(s) in RCA: 284] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
It is well recognized that consumption of alcohol leads to liver disease in a dose-dependent manner; however, the exact mechanisms remain unclear. Hypoxia subsequent to a hypermetabolic state may be involved; therefore, when it was observed recently that inactivation of Kupffer cells prevented stimulation of hepatic oxygen uptake by alcohol, the idea that Kupffer cells participate in early events that ultimately lead to alcohol-induced liver disease became a real possibility. The purpose of this study was to test that hypothesis. Male Wistar rats were exposed to ethanol continuously by means of intragastric feeding for up to 4 weeks using the model developed by Tsukamoto and French. In this model, ethanol causes fatty liver, necrosis and inflammation--changes characteristic of alcohol-induced liver disease in human beings. Kupffer cells were inactivated by twice weekly treatment with gadolinium chloride (GdCl3), a selective Kupffer cell toxicant. AST levels were elevated to 192 +/- 13 and 244 +/- 56 IU/L in rats exposed to ethanol for 2 and 4 wk, respectively (control value, 88 +/- 7). This injury was prevented almost completely by GdCl3 treatment. Fatty changes, inflammation and necrosis were also all reduced dramatically by GdCl3 treatment. The average hepatic pathological score of rats treated with ethanol for 4 wk was 4.3 +/- 0.6, which was reduced significantly in ethanol- and GdCl3-treated rats to 1.8 +/- 0.5 (p < 0.05). Rates of ethanol elimination were elevated 2- to 3-fold in rats exposed to ethanol for 2 to 4 wk. This elevation was blocked by GdCl3 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- Y Adachi
- Department of Pharmacology, University of North Carolina at Chapel Hill 27599-7365
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Lichtman SN, Bachmann S, Munoz SR, Schwab JH, Bender DE, Sartor RB, Lemasters JJ. Bacterial cell wall polymers (peptidoglycan-polysaccharide) cause reactivation of arthritis. Infect Immun 1993; 61:4645-53. [PMID: 8406862 PMCID: PMC281216 DOI: 10.1128/iai.61.11.4645-4653.1993] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Intraperitoneal (i.p.) injection of peptidoglycan-polysaccharide derived from group A streptococci (PG-APS) causes chronic arthritis with spontaneous remissions and exacerbations. We hypothesized that, following i.p. injection, PG-APS released from hepatic stores mediated spontaneous recurrences of arthritis. We tested whether transplanted livers with large amounts of PG-APS were able to reactivate quiescent arthritis. Saline-loaded (group 1) or PG-APS-loaded (group 2) livers were transplanted into rats which had been injected intra-articularly 10 days earlier with PG-APS in one joint and saline in the other. A comparison was made with the arthritis that occurred in rats injected i.p. with PG-APS which did not receive transplants (group 3). Arthritis was monitored by serial measurement of joint diameters. Transplantation of saline-loaded livers (group 1) caused no reactivation of arthritis. However, transplantation of PG-APS-loaded livers (group 2) reactivated arthritis (P < 0.0001). Injection of PG-APS i.p. (group 3) induced the most-severe arthritis. PG-APS levels in plasma decreased with time, and PG-APS accumulated in the spleen in groups 2 and 3. Plasma and hepatic levels of PG-APS in rats injected i.p. with PG-APS were greater than levels in rats transplanted with PG-APS-loaded livers, which in turn were greater than levels in rats with saline-loaded livers. Plasma tumor necrosis factor did not correlate with recurrence of arthritis. Transplantation with PG-APS-loaded livers induced reactivation of arthritis in preinjured joints. The extent of arthritis was proportional to hepatic PG-APS content. Reactivation of arthritis may be mediated by slow release of liver-sequestered PG-APS or cytokines (not tumor necrosis factor) released by the liver.
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Affiliation(s)
- S N Lichtman
- Department of Pediatrics, University of North Carolina, Chapel Hill 27599-7220
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Bond JM, Chacon E, Herman B, Lemasters JJ. Intracellular pH and Ca2+ homeostasis in the pH paradox of reperfusion injury to neonatal rat cardiac myocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:C129-37. [PMID: 8338121 DOI: 10.1152/ajpcell.1993.265.1.c129] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Ischemia is characterized by anoxia and a large decrease of tissue pH. After a critical period of ischemia, reperfusion precipitates irreversible injury. Previous work showed that reperfusion injury to cultured neonatal myocytes was precipitated by a rapid return to physiological pH, a "pH paradox" (Bond, J., B. Herman, and J. Lemasters. Biochem. Biophys. Res. Commun. 179: 798-803, 1991). The aim of this study was to measure intracellular pH (pHi) and cytosolic free Ca2+ during the pH paradox of reperfusion injury to cultured neonatal rat cardiac myocytes. pHi and free Ca2+ were measured by ratio imaging of 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and fura 2 fluorescence. To simulate ATP depletion and acidosis of ischemia, myocytes were incubated with 20 mM 2-deoxyglucose plus 2.5 mM NaCN at pH 6.2. During simulated ischemia, pHi dropped to < 6.5 and subsequently remained constant. During this time, some blebbing but little hypercontraction occurred. After 3 or 4 h of simulated ischemia, inhibitors were removed and cells were incubated at pH 7.4 to simulate reperfusion. pHi began to increase, blebbing accelerated, and myocytes hypercontracted. As pHi increased, viability was lost. The same occurred if pH was increased but metabolic inhibitors were not removed. Monensin, a Na(+)-H+ ionophore, accelerated the increase of pH after reperfusion and hastened cell killing. Hypercontraction, blebbing, and loss of viability did not occur when inhibitors were removed at pH 6.2 or in the presence of dimethylamiloride, an inhibitor of Na(+)-H+ exchange. Protection was associated with maintenance of an acidotic pHi. Free Ca2+ progressively increased during simulated ischemia. After simulated reperfusion, free Ca2+ increased further.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J M Bond
- Department of Cell Biology and Anatomy, School of Medicine, University of North Carolina, Chapel Hill 27599-7090
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